## What is "Dependency Injection"

**"Dependency Injection"** means, in programming, that there is a way for your code (in this case, your *path operation functions*) to declare things that it requires to work and use: "dependencies".

You can declare that a parameter can accept `None`, but that it's still required. This would force clients to send a value, even if the value is `None`.

To do that, you can declare that `None` is a valid type but still use `...` as the default:

//// tab | Python 3.10+

```Python hl_lines="9"
{!> ../../docs_src/query_params_str_validations/tutorial006c_an_py310.py!}
```

////

//// tab | Python 3.9+

  }

  /**
   * Returns the {@link Method} instance for {@link #testAddAll_unsupportedNonePresent()} so that
   * tests can suppress it with {@code FeatureSpecificTestSuiteBuilder.suppressing()} while we
   * figure out what to do with <a

# Security Tools

When you need to declare dependencies with OAuth2 scopes you use `Security()`.

But you still need to define what is the dependable, the callable that you pass as a parameter to `Depends()` or `Security()`.

There are multiple tools that you can use to create those dependables, and they get integrated into OpenAPI so they are shown in the automatic docs UI, they can be used by automatically generated clients and SDKs, etc.

                          Apache Maven

  What is it?
  -----------

  Maven is a software project management and comprehension tool. Based on
  the concept of a Project Object Model (POM), Maven can manage a project's
  build, reporting and documentation from a central piece of information.

  Documentation
  -------------

  The most up-to-date documentation can be found at https://maven.apache.org/.

  Release Notes
  -------------

code is a library, we strongly recommend using the [Guava Beta Checker] to
ensure that you do not use any `@Beta` APIs!**

[Guava Beta Checker]: https://github.com/google/guava-beta-checker

<!-- References -->

  // ResourceRules describes what operations on what resources/subresources the ValidatingAdmissionPolicy matches.
  // The policy cares about an operation if it matches _any_ Rule.
  // +listType=atomic
  // +optional
  repeated NamedRuleWithOperations resourceRules = 3;

  // ExcludeResourceRules describes what operations on what resources/subresources the ValidatingAdmissionPolicy should not care about.

# Deployment

Deploying a **FastAPI** application is relatively easy.

## What Does Deployment Mean

To **deploy** an application means to perform the necessary steps to make it **available to the users**.

For a **web API**, it normally involves putting it in a **remote machine**, with a **server program** that provides good performance, stability, etc, so that your **users** can **access** the application efficiently and without interruptions or problems.

## Context Managers

### What are "Context Managers"

"Context Managers" are any of those Python objects that you can use in a `with` statement.

      required: true
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